1. Field of the Invention
This invention relates to a liquid discharging head for discharging desired liquid by the creation of bubbles caused by making heat energy act on the liquid, a method of manufacturing the liquid discharging head, a head cartridge carrying the liquid discharging head thereon and a liquid discharging apparatus. The invention particularly relates to a liquid discharging head having a movable member displaceable by the utilization of the creation of bubbles, a method of manufacturing the liquid discharging head, a head cartridge carrying the liquid discharging head thereon and a liquid discharging apparatus.
The word "recording" in the present invention means not only imparting images having meanings such as characters and figures to a recording medium, but also imparting images having no meaning such as patters to the recording medium.
2. Related Background Art
There is known an ink jet recording method, i.e., a so-called bubble jet recording method of giving energy such as heat to ink to thereby create in the ink a state change resulting in a steep volume change (creation of a bubble), discharging the ink from a discharge port by an acting force based on the state change, causing the ink to adhere onto a recording medium and effecting image formation. A recording apparatus using this bubble jet recording method, as disclosed in Japanese Patent Publication No. 61-59911 and Japanese Patent Publication No. 61-59914, is generally provided with a discharge port for discharging ink therefrom, an ink flow path communicating with this discharge port, and a heating member (electro thermal converting member) as energy generating means disped in the ink flow path for discharging the ink.
According to the recording method as described above, images of high dignity can be recorded at a high speed and with low noise and also, in a head for carrying out this recording method, discharge ports for discharging the ink therefrom can be disposed highly densely, and this leads to many excellent points that recorded images of high resolution and further, color images can be easily obtained by a compact apparatus, etc. In recent years, this bubble jet recording method has been utilized in many office instruments such as printers, copying apparatuses and facsimile apparatuses, and has come to be utilized even in an industrial system such as a textile printing apparatus.
So, some of the inventors have returned to the principle of liquid discharge and have energetically carried out researches to provide a novel liquid discharging method utilizing bubbles which could heretofore not be obtained and a head or the like used therein, and filed Japanese Patent Laid-Open Application No. 9-201966, etc.
A prior-art liquid discharging method disclosed in Japanese Patent Laid-Open Application No. 9-201966, etc. and a head used therein will now be described with reference to FIGS. 12A to 12D, etc. of the accompanying drawings. FIGS. 12A to 12D illustrate the principle of discharge in the prior-art liquid discharging head, and is a cross-sectional view in the direction of a liquid flow path. FIG. 13 is a fragmentary broken-away perspective view of the liquid discharging head shown in FIGS. 12A to 12D. The liquid discharging head shown in FIGS. 12A to 12D and FIG. 13 is of the most basic construction in which when liquid is to be discharged, the direction of propagation of pressure based on a bubble and the direction of growth of the bubble are controlled to thereby improve discharging force and discharging efficiency.
The words "upstream" and "downstream" used in the following description are represented as expressions with respect to the direction of flow of liquid going from a supply source of liquid toward discharge ports via above a bubble creating area (or a movable member), or with respect to the direction in this construction.
The "downstream side" with respect to the bubble itself represents the discharge port side portion of the bubble which is regarded as directly acting on chiefly the discharge of a liquid droplet. More specifically, it means a bubble created at the downstream side with respect to the direction of flow or the direction in the construction, relative to the center of the bubble, or an area downstream of the center of the area of a heat generating member.
Further, "comb-teeth" means a shape in which the fulcrum portion of the movable member is a common portion and the front of the free end thereof is opened.
In the example shown in FIGS. 12A to 12D, the liquid discharging head is such that as a discharge energy generating element for discharging the liquid, a heating member 102 for making heat energy act on the liquid (in the present example, a heat generating resistance member of a shape of 40 .mu.m.times.105 .mu.m) is provided on an element substrate 101 and liquid flow paths 103 are disposed on the element substrate 101 correspondingly to the heating member 102. The liquid flow paths 103 communicate with discharge ports 104 and also communicate with a common liquid chamber 105 for supplying the liquid to the plurality of liquid flow paths 103, and receive from this common liquid chamber 105 an amount of liquid corresponding to the liquid discharged from the discharge ports 104.
On the element substrate 101 for these liquid flow paths 103, a plate-like movable member 106 formed of a resilient material such as a metal and having a flat portion is provided in a cantilever fashion so as to be opposed to the aforementioned heating member 102. One end of this movable member 106 is fixed to a pedestal (support member) 107 or the like formed by patterning photosensitive resin or the like on the wall of the liquid flow paths 103 or the element substrate 101. Thereby, the movable member 106 is held on the pedestal 107, and a fulcrum (fulcrum portion) 108 is constituted.
Also, by making the movable member 106 comb-teeth-like, the movable member 106 can be made simply and inexpensively, and the alignment thereof with the pedestal 107 can be done easily.
This movable member 106 is disposed at a distance of the order of 15 um from the heating member 102 in such a manner as to cover the heating member 102 at a location facing the heating member 102 so as to have the fulcrum (fulcrum portion: fixed end) 108 upstream of a great flow flowing from the common liquid chamber 105 to the discharge port 104 side via above the movable member 106 by the discharging movement of the liquid, and have a free end (free end portion) 109 downstream with respect to the fulcrum 108. The space between the heating member 102 and the movable member 106 provides a bubble creating area 110.
The heating member 102 is caused to generate heat to thereby make the heat act on the liquid in the bubble creating area 110 between the movable member 106 and the heating member 102, thus causing the liquid to create a bubble 111 based on a film boiling phenomenon as described in U.S. Pat. No. 4,723,129, etc. (see FIG. 12B). Pressure based on the creation of the bubble 111 and the bubble 111 preferentially act on the movable member 106, which is thus displaced so as to be greatly opened toward the discharge port 104 side about the fulcrum 108, as shown in FIGS. 12B and 12C or FIG. 13. By the displacement or displaced state of the movable member 106, the propagation of the pressure based on the creation of the bubble 111 or the growth of the bubble 111 itself is directed to the discharge port 104 side. Also, at this time, the bubbling power of the bubble 111 becomes easy to direct to the discharge port 4 side because the tip end portion of the free end 109 has a width, and a fundamental improvement in the discharging efficiency and discharging force or discharging speed of a liquid droplet can be achieved.
As described above, the technique disclosed in Japanese Patent Laid-Open Application No. 9-201966, etc. is the technique of positively controlling the bubble by making the positional relation between the fulcrum and the free end of the movable member in the liquid path into a relation in which the free end is located at the discharge port side, i.e., the downstream side, and disposing the movable member in face-to-face relationship with the heating member or the bubble creating area.
As described above, the pedestal is provided on the fixed portion of the movable member, whereby a gap of the order of 1 to 20 .mu.m is formed between the movable member and the heating member, and the effect of improving the liquid discharging efficiency by the movable member is sufficiently derived. Thus, according to a liquid discharging head or the like based on the very novel principle of discharge as described above, the combined effect of the bubble created and the movable member displaced thereby can be obtained and the liquid near the discharge port can be efficiently discharged and therefore, the liquid discharging efficiency is improved as compared with the discharging method and head of the prior-art bubble jet type.
While various materials are conceivable as the material of the movable member used in the above-described liquid discharging head, nickel which is excellent in resiliency is generally used in order to efficiently utilize the pressure by the creation of the bubble for the discharging of the liquid.
However, the adoption of a construction in which a pedestal is provided on the fixed portion of the movable member in the liquid discharging head leads to the inconvenience that the step of forming the movable member becomes complicated. Also, when in such construction, an attempt is made to firmly effect the fixing of the movable member, it is necessary to secure a certain degree of length of the pedestal portion in the direction of ink flow, but if the pedestal thus becomes long, the pedestal will occupy a portion of the flow paths or the liquid chamber, and this has led to the fear that, particularly when it is desired to make the head compact or the flow paths are arranged very densely, the ink supply characteristic cannot be sufficiently displayed.